Device and method for the optically exciting laser-active crystals with polarization-dependent absorption

Abstract

A device for the optical excitation of laser-active crystals with a diode laser ( 1 ) is disclosed. The diode laser ( 1 ) generates pump radiation ( 2 ), and the laser-active crystal ( 14 ) is arranged in a solid-state laser or solid-state laser amplifier. The laser-active crystal ( 14 ) has an axis (C) with strong absorption and an axis (A) with weak absorption. The pump radiation ( 2 ) from the diode laser ( 1 ) is substantially polarised linearly in a privileged polarisation direction. The device is configured in such a way that the pump radiation ( 2 ) is injected into the laser-active crystal ( 14 ) with a polarisation direction which is oriented parallel to the weak-absorption axis (A). The polarisation of the pump radiation in the vicinity of the laser-active crystal is oriented parallel relative to the weak-absorption axis.

1. Device for the optical excitation of laser-active crystals, with a diode laser ( 1 ) which generates pump radiation ( 2 ), the laser-active crystal being arranged in a solid-state laser or solid-state laser amplifier and the laser-active crystal having an axis (C) with strong absorption and an axis (A) with weak absorption, comprising: an optical element ( 4 ) is arranged downstream of the diode laser ( 1 ) in order to achieve spatial shaping of the pump radiation from the diode laser ( 1 ) and in that the pump radiation ( 2 ) from the diode laser ( 1 ) is substantially polarised linearly in a privileged polarisation direction, and in that the polarisation direction of the pump radiation ( 2 ) is oriented parallel to the weak-absorption axis (A) of the laser-active crystal ( 14 ) when it is incident in the laser-active crystal ( 14 ); and
 wherein the laser-active crystal ( 14 ) has at least a first and a second end face ( 14   a ,  14   b ) which have a polarisation-dependent transmission, and in that the polarisation direction of the pump radiation ( 2 ) is oriented so that the reflection losses at the first or second end faces ( 14   a ,  14   b ) are minimal and the optical power which enters the laser-active crystal ( 14 ) is maximal. 
 
   
   
     2. Device for the optical excitation of laser-active crystals, with a diode laser ( 1 ) which generates pump radiation ( 2 ), the laser-active crystal being arranged in a solid-state laser or solid-state laser amplifier and the laser-active crystal having an axis (C) with strong absorption and an axis (A) with weak absorption, comprising: an optical element ( 4 ) is arranged downstream of the diode laser ( 1 ) in order to achieve spatial shaping of the pump radiation from the diode laser ( 1 ) and in that the pump radiation ( 2 ) from the diode laser ( 1 ) is substantially polarised linearly in a privileged polarisation direction, and in that the polarisation direction of the pump radiation ( 2 ) is oriented parallel to the weak-absorption axis (A) of the laser-active crystal ( 14 ) when it is incident in the laser-active crystal ( 14 ); and
 wherein the solid-state laser or solid-state laser amplifier comprises a laser resonator ( 27 ) with a multiplicity of mirrors ( 28 ,  29 ,  30 ), the surfaces of which are provided with polarisation-dependent transmission, and in that the polarisation direction of the pump radiation ( 2 ) is oriented so that the reflection losses at these surfaces are minimal and the optical power which enters the laser-active crystal ( 14 ) is maximal. 
 
   
   
     3. Device according to  claim 2 , wherein the laser-active crystal ( 14 ) consists of Nd:YV 0   4 , Nd:GdVO 4 , Nd:LSB, Nd:YA 10   3 , Nd.:YLF or Nd:BEL. 
   
   
     4. Device according to  claim 2 , wherein the laser-active crystal ( 14 ) consists of Nd:YV 0   4  with neodymium doping of more than 0.5% (at.). 
   
   
     5. Device according to  claim 2 , wherein the optical element ( 4 ) is configured in the form of microoptics. 
   
   
     6. Device for the optical excitation of laser-active crystals, with a diode laser ( 1 ) which generates pump radiation ( 2 ), the laser-active crystal being arranged in a solid-state laser or solid-state laser amplifier and the laser-active crystal having an axis (C) with strong absorption and an axis (A) with weak absorption, comprising: an optical element ( 4 ) is arranged downstream of the diode laser ( 1 ) in order to achieve spatial shaping of the pump radiation from the diode laser ( 1 ) and in that the pump radiation ( 2 ) from the diode laser ( 1 ) is substantially polarised linearly in a privileged polarisation direction, and in that the polarisation direction of the pump radiation ( 2 ) is oriented parallel to the weak-absorption axis (A) of the laser-active crystal ( 14 ) when it is incident in the laser-active crystal ( 14 ); and
 wherein the optical element ( 4 ) is designed in the form of a polarisation-preserving waveguide, in order to achieve spatial shaping of the pump radiation ( 2 ) from the diode laser ( 1 ), the polarisation-dependent waveguide consisting, for example, of a glass rod or an optical fibre. 
 
   
   
     7. Device for the optical excitation of laser-active crystals, with a diode laser ( 1 ) which generates pump radiation ( 2 ), the laser-active crystal being arranged in a solid-state laser or solidstate laser amplifier and the laser-active crystal having an axis (C) with strong absorption and an axis (A) with weak absorption, comprising: an optical element ( 4 ) is arranged downstream of the diode laser ( 1 ) in order to achieve spatial shaping of the pump radiation from the diode laser ( 1 ) and in that the pump radiation ( 2 ) from the diode laser ( 1 ) is substantially polarised linearly in a privileged polarisation direction, and in that the polarisation direction of the pump radiation ( 2 ) is oriented parallel to the weak-absorption axis (A) of the laser-active crystal ( 14 ) when it is incident in the laser-active crystal ( 14 );
 wherein the second end face ( 14   b ) of the laser-active crystal ( 14 ) is assigned a reflector ( 52 ), which reflects the unabsorbed pump radiation ( 50 ) that was injected through the first end face ( 14   a ), and injects it into the second end face ( 14   b ) as reflected pump radiation ( 54 ); and 
 wherein the laser-active crystal ( 14 ) has doping and a length which are selected so that less than 70% of the pump radiation ( 2 ) can be absorbed in the laser-active crystal ( 14 ) after entering through the first end face ( 14   a ). 
 
   
   
     8. Device according to  claim 7 , wherein approximately 50 to 60% of the pump radiation ( 2 ) can be absorbed in the laser-active crystal ( 14 ) after entering through the first end face ( 14   a ). 
   
   
     9. Method for the optical excitation of laser-active crystals with a diode laser ( 1 ), the laser-active crystal ( 14 ) being arranged in a solid-state laser or solid-state laser amplifier, comprising:
 spatially shaping pump radiation ( 2 ) generated by the diode laser ( 1 ) with an optical element ( 4 ), the shaped pump radiation ( 2 ) having a polarisation direction, and 
 projection onto a laser-active crystal ( 14 ), which has an axis (C) with strong absorption and an axis (A) with weak absorption, so that the polarisation direction of the pump radiation ( 2 ) is oriented parallel to the weak-absorption axis (A) of the laser-active crystal ( 14 ); and 
 wherein the laser-active crystal ( 14 ) has at least a first and a second end face ( 14   a ,  14   b ) which have a polarisation-dependent transmission, and in that the polarisation direction of the pump radiation ( 2 ) is oriented so that the reflection losses at the first or second end faces ( 14   a ,  14   b ) are minimal and the optical power which enters the laser-active crystal ( 14 ) is maximal. 
 
   
   
     10. Method for the optical excitation of laser-active crystals with a diode laser ( 1 ), the laser-active crystal ( 14 ) being arranged in a solid-state laser or solid-state laser amplifier, comprising:
 spatially shaping pump radiation ( 2 ) generated by the diode laser ( 1 ) with an optical element ( 4 ), the shaped pump radiation ( 2 ) having a polarisation direction, and 
 projection onto a laser-active crystal ( 14 ), which has an axis (C) with strong absorption and an axis (A) with weak absorption, so that the polarisation direction of the pump radiation ( 2 ) is oriented parallel to the weak-absorption axis (A) of the laser-active crystal ( 14 ); and 
 wherein the solid-state laser or solid-state laser amplifier comprises a laser resonator ( 27 ) with a multiplicity of mirrors ( 28 ,  29 ,  30 ), the surfaces of which are provided with polarisation-dependent transmission, and in that the polarisation direction of the pump radiation ( 2 ) is oriented so that the reflection losses at these surfaces are minimal and the optical power which enters the laser-active crystal ( 14 ) is maximal. 
 
   
   
     11. Method according to  claim 10 , wherein the laser-active crystal ( 14 ) consists of Nd:YV 0   4 , Nd:GdVO 4 , Nd:LSB, Nd:YA 10   3 , Nd:YLF or Nd:BEL. 
   
   
     12. Method according to  claim 10 , wherein the laser-active crystal ( 14 ) consists of Nd:YV 0   4  with neodymium doping of more than 0.5% (at.). 
   
   
     13. Method for the optical excitation of laser-active crystals with a diode laser ( 1 ), the laser-active crystal ( 14 ) being arranged in a solid-state laser or solid-state laser amplifier, comprising:
 spatially shaping pump radiation ( 2 ) generated by the diode laser ( 1 ) with an optical element ( 4 ), the shaped pump radiation ( 2 ) having a polarisation direction, and 
 projection onto a laser-active crystal ( 14 ), which has an axis (C) with strong absorption and an axis (A) with weak absorption, so that the polarisation direction of the pump radiation ( 2 ) is oriented parallel to the weak-absorption axis (A) of the laser-active crystal ( 14 ); 
 wherein pump radiation ( 52 ) emerging from the second end face ( 14   b ) of the laser-active crystal ( 14 ) is reflected by a a reflector ( 52 ), and re-enters the laser active crystal ( 14 ) as reflected pump radiation ( 54 ) through the second end face ( 14   b ); and 
 wherein the laser-active crystal ( 14 ) has doping and a length which are selected so that less than 70% of the pump radiation ( 2 ) can be absorbed in the laser-active crystal ( 14 ) after entering through the first end face ( 14   a ). 
 
   
   
     14. Method according to  claim 13 , wherein approximately 50 to 60% of the pump radiation ( 2 ) is absorbed in the laser-active crystal ( 14 ) after entering through the first end face ( 14   a ).